Use either a late lane merge system or an early lane merge system, but not both, based on agency goals and objectives for improving work zone operations.

This study tested the use of a dynamic lane merge system (DLMS) installed at three work zones on I-94 and I-64 in Michigan during the 2006 construction season. The system used microwave traffic sensors, wireless communications, and a series of portable dynamic message signs (DMS) to advise drivers of definite merge points when average traffic speeds dropped below pre-set threshold levels.

Traffic performance data collected with and without the system indicated the system improved traffic flow and reduced delay. Researchers documented several lessons learned during the project and provided recommendations for future implementers.

Lesson Learned

Use either a late lane merge system or an early lane merge system, but not both. Late lane merge systems are recommended where the goal is to minimize delay and reduce queue length. Early lane merge systems are recommended at sites where queue length is not a problem, but the goal is to minimize delay and reduce aggressive driving.

Confirm pre-construction traffic volumes are large enough to warrant treatment. Both early and late lane merge systems are most effective on segments of freeways that experience moderate to heavy congestion. Since some drivers may choose to take alternate routes to avoid the area pre-construction traffic volumes may be slightly higher than those observed during the construction period. For a two-to-one lane reduction, the following traffic volumes were recommended:

Dynamic Early Lane Merge System

Average daily traffic: 21,500 to 34,500 vehicles per day, per direction

Average weekday peak period volumes prior to construction: 2,000 to 3,000 vehicles per hour, per direction.

Dynamic Late Lane Merge System

Average daily traffic: at least 22,500 vehicles per day, per direction

Average weekday peak period volumes prior to construction: at least 1,800 vehicles per hour, per direction.

Educate drivers on the purpose and benefits of work zone ITS. A media campaign should accompany the implementation.

Allow sufficient lead time for drivers approaching a work zone to react to highway advisory radio (HAR). The first roadside message that advises drivers to use HAR information should be located far enough upstream from the work zone to allow drivers to find the channel and listen to the entire message at least once prior to entering the work zone control area.

Two DMS should be installed near the lane closure taper. In addition to the placement of static message signs at work zones, two portable DMS should be placed near the lane closure taper (one on each shoulder) to enable drivers to see the messages when views may be obstructed by large trucks.

Dynamic lane merge systems should activate at a threshold speed of 35 mi/hr. Trigger speeds of 35 mi/hr and 45 mi/hr were both used during the field test. Driver conformance was higher at a trigger speed of 35 mi/hr.

Traffic sensors should monitor speed and traffic volume at the lane closure taper.

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